In the field of Occupational Safety and Health, respirators (respiratory personal protective equipment, RPPE) have been widely used in industry. More recently, the possibility of bioterrorism and/or epidemics as well as the perception of risk increase the likelihood of much more widespread respirator use. Persons with mild respiratory impairments or individuals who develop mild respiratory impairments as a consequence of terrorism and/or epidemic may be required to use respirators rather than being excluded from manyjobs. This project will extend prior research about respirator effects in relatively healthy individuals to personswith mild respiratory impairments. Four groups of subjects will be studied: normal, COPD, chronic rhinitis, asthma. Each subject will be studied in a controlled exercise laboratory using respirator surrogateloads (inspiratory resistance, expiratory resistance, dead space). In addition, each will be studied during simulated "real world" work of a sedentary or moderate exertion level using an N95 and a full face mask respirator. Measures will include physiologic parameters, subjective ratings, and estimates of proper utilization. Over three years, approximately 140 subjects will participate. The project should characterize the response patterns of these individual groups as well as delineate the effects of different components of respirator loads. The information may be useful for policy establishment (e.g., shelter in place vs. respirator use), designing better respirators, and worker selection/counseling.